* Chicken or the egg — a seemingly unbreakable cycle of causation, which has an unknown origin.
* Cornelian dilemma — a choice between actions which will all have a detrimental effect on the chooser or on someone they care for.
* Deadlock — in computing, when two processes reach a standstill or impasse; paradoxically waiting for the other to finish.
* Double bind — a forced choice between two logically conflicting demands.
* Hobson’s choice — the choice between taking an option or not taking it.
* Lesser of two evils principle — a choice between two undesirable outcomes.
* Morton’s Fork — a choice between two equally unpleasant alternatives.
* Paradox — a statement or group of statements that leads to a contradiction or a situation which defies intuition.